Ortho-cyanophenyl biphenylcarboxylate liquid crystal esters and mixtures thereof

Abstract

A number of alkyl and alkoxy-substituted ortho-cyanophenyl biphenylcarboxylate esters have been prepared for use as components for nematic liquid crystal mixtures which can be used in homeotropically aligned, field effect display devices or in dynamic scattering displays. These materials have large negative dielectric anisotropies and high birefringence.

What is claimed is: 
     
       1. Alkyl and alkoxy-substituted ortho-cyanophenyl biphenylcarboxylate esters whose structural formula are: ##STR3## wherein R and R' are hydrogen or an alkyl group of the formula C n  H 2n+1  and R" is an alkyl group of the formula C n  H 2n+1  where n ranges from 1 to 8. 
     
     
       2. A compound of claim 1 whose structure is I and R is hydrogen. 
     
     
       3. A compound of claim 1 whose structural formula is I and R is C 4  H 9 . 
     
     
       4. A compound of claim 1 whose structure is II and R' and R" are defined in claim 1. 
     
     
       5. A compound of claim 4 wherein R' is C 4  H 9  and R" is C 5  H 11 . 
     
     
       6. A nematic liquid crystal mixture exhibiting a high birefringence and a large negative dielectric anisotropy comprising a compound whose formula is ##STR4## wherein R' and R" are alkyl groups whose formula are C n  H 2n+1  where n ranges from 1 to 8, which possess a large negative dielectric anisotropy, and a nematic liquid crystal mixture that possesses a positive dielectric anisotropy. 
     
     
       7. A liquid crystal mixture of claim 6 wherein said positive dielectric anisotropy mixture is comprised of p-methyoxy-p'-pentyltolane and p-propoxy-p'-heptyltolane.